This passage is from The Weight of Glory by C.S. Lewis. Though some may take exception to the idea that Christians aren’t automatically forgiven for all sins, he makes a very good Biblical point.
We say a great many things in church (and out of church too) without thinking of what we are saying. For instance, we say in the Creed “I believe in the forgiveness of sins.” I had been saying it for several years before I asked myself why it was in the Creed. At first sight it seems hardly worth putting in. “If one is a Christian,” I thought, “of course one believes in the forgiveness of sins. It goes without saying.” But the people who compiled the Creed apparently thought that this was a part of our belief which we needed to be reminded of every time we went to church. And I have begun to see that, as far as I am concerned, they were right. To believe in the forgiveness of sins is not nearly so easy as I thought. Real belief in it is the sort of thing that very easily slips away if we don’t keep on polishing it up.
We believe that God forgives us our sins; but also that He will not do so unless we forgive other people their sins against us. There is no doubt about the second part of this statement. It is in the Lord’s Prayer; was emphatically stated by our Lord. If you don’t forgive you will not be forgiven. No part of His teaching is clearer, and there are no exceptions to it. He doesn’t say that we are to forgive other people’s sins provided they are not too frightful, or provided there are extenuating circumstances, or anything of that sort. We are to forgive them all, however spiteful, however mean, however often they are repeated. If we don’t, we shall be forgiven none of our own.
The Scripture passage to which he referred is from Matthew 6:11-15. One could try to dispute Lewis’ conclusion, but the Lord was pretty clear about it. Maybe you will tell me that He was speaking at that moment from the Law Dispensation, since He hadn’t as yet performed His Redemptive Act.
I’m afraid that goose won’t fly, friend. As with the balance of His Sermon on the Mount, Jesus spoke from the only perspective he had, that of grace. Why would He speak from the Law’s perspective when He would, in a short time, fulfill the Law?
If you insist on the Law idea, what about First Corinthians’ love chapter? Remember all the awful things St. Paul did before he met Jesus? Loving forgiveness did not come naturally to that Pharisee. He had hated Christians and Gentiles, but he taught unconditional love to the Corinthian church.
Nope, if you harbor a grudge, refusing to love and forgive anyone, you can’t expect Jesus’ blood to cover your unconfessed sin. Otherwise, you’d be no better off than members of the Islamic State or the KKK. Is your grudge worth that?